Work hardening of tungsten alloy rods is typically conducted using a swaging process. In the swaging process, the rod is work hardened, i.e., reduced in diameter, in one or more steps to achieve the desired material properties for a given application. However, for certain applications where tight tolerances are mandated, the swaging process is inefficient because it cannot consistently produce the desired material properties nor can it produce rods having strict dimensional tolerances without additional finishing steps. For example, ultimate tensile strength and yield strength may vary by 15 Ksi and total diameter by .+-.0.003 inch. Variations in the material properties and in the dies used in the swager during the metal working operation are the principal causes of these inefficiencies. To achieve the necessary diametrical control when swaging is used, the rods have to be left oversized so that they can be ground to the required diameter, a step which yields about 5% scrap. This finishing work adds to the cost of manufacturing by increasing both labor and materials costs.
Thus, it would be an advantage to have a process whereby tungsten alloy rods could be more efficiently and consistently work hardened while achieving a greater degree of diametrical control.